Brain Stimulation as a Treatment for Apathy: A Scoping Review of Effects and Safety

OBJECTIVE: Apathy is a neuropsychiatric syndrome characterized by impairment of goal-directed behavior, cognition, and emotional responsiveness. In this scoping review, the authors evaluated the literature on brain stimulation for the treatment of patients with apathy across diagnostic categories and provide recommendations to guide future research and practice. METHODS: The authors searched PubMed, Scopus, and PsycInfo for studies involving brain stimulation for apathy as a primary or secondary outcome. RESULTS: From 1,209 records, 52 studies evaluating brain stimulation were included; of these, 10 systematic reviews or meta-analyses were synthesized separately. Modalities included repetitive transcranial magnetic stimulation (rTMS; N=26), deep brain stimulation (DBS; N=7), transcranial direct current stimulation (tDCS; N=6), electroconvulsive therapy (N=1), transcranial alternating current stimulation (N=1), and transcranial pulsating electromagnetic field therapy (N=1). Populations included patients with schizophrenia (N=477), Parkinson's disease (PD; N=289), depression (N=288), Alzheimer's disease (AD) and mild cognitive impairment (MCI) (N=210), Huntington's disease (N=42), PD with MCI (N=28), traumatic brain injury (N=28), stroke (N=14), COVID-19 (N=12), and dementia with Lewy bodies (N=6) (total N=1,366). rTMS improved apathy measures, most consistently in AD, with positive trends in depression, MCI, stroke, and schizophrenia. tDCS showed variable effects, with some benefits for schizophrenia. DBS showed mixed results, varying with stimulation location. Observed adverse events were mild and modality specific. CONCLUSIONS: Investigations into brain stimulation as a treatment for apathy show some promise. Conclusions were limited by small sample sizes, heterogeneous study designs, and variable outcome measures. Randomized trials with common validated apathy instruments, standardized stimulation parameters, and harmonized diagnostic measures may help advance the field.